Underwater power source



Dec; 31, 1968 R. P. VINCENT E 3,418,313

UNDERWATER POWER SOURCE .rlll ilfll Filed April 22, 1966 RENIC P VINCENT LAWRENCE B. WILDER INVENTOR.

BY ATTORNEY o g E m/ R. E

Dec. 31, 1968 R. P. VINCENT ET AL 3,418,818

UNDERWATER POWER SOURCE Filed April 22, 1966' Sheet 2 of 2,

' LOW PRESSURE FIG. 3

HIGH PRESSURE RENIC F? VINCENT LAWRENCE B. WILDER INVENTOR.

BY A? M ATTORNEY United States Patent 3,418,818 UNDERWATER POWER SOURCE Renic P. Vincent and Lawrence B. Wilder, Tulsa, Okla., assignors to Pan American Petroleum Corporation, Tulsa, Okla., a corporation of Delaware Filed Apr. 22, 1966, Ser. No. 544,434 11 Claims. (Cl. 6169) ABSTRACT OF THE DISCLOSURE A method and apparatus for supplying power to underwater apparatuses which makes use of the head of water at the depth of the apparatus to drive a hydraulic motor. A lower pressure container is provided to receive discharge water from the hydraulic motor. Means are further provided to rejuvenate the low pressure container.

This invention relates to apparatus for carrying out operations at underwater installations such, for example, as at an underwater wellhead, an underwater oil and gas producing facility or storage and the like. It relates particularly to a novel way of supplying power for such underwater apparatus.

The search for oil and gas has in recent years led to the drilling of many wells in water-covered areas. In fact, many of our more prolific oil and gas wells have been discovered in such marine locations. Many of the wells for the development of such fields may be drilled in water up to 600 feet or more in depth. These developments of offshore locations are resulting in the installation of large amounts of underwater equipment used in producing the oil and gas fields. Many of these installations are at depths below that at which divers can safely work. Therefore use has been made of what is known as an underwater manipulator in installing underwater equipment on the ocean floor for such wells or for carrying out workover operations underwater at any of the various ocean floor installations.

The manipulator may take various forms but usually includes a compartment maintained at near atmospheric pressure for the operator and is further provided with robot-like arms extending from the exterior of the compartment for performing various operations such as holding equipment, tightening or loosening bolts and the like. One such underwater manipulator is shown in US. Patent 3,165,899.

One of the major problems in the use of such underwater manipulators is that of providing an adequate power source for the various operations of the manipulator. Electrical storage batteries provide the most common means of power. However, these batteries add considerably to the bulk and weight as well as to the cost of such manipulators or vessels containing such manipulators.

It is an object of this invention to provide a novel means for supplying power for underwater manipulators.

In a preferred embodiment, an underwater vehicle which has a body structure for supporting the manipulator arms is provided with a high strength container (in addition to the operators compartment) which is able to withstand great pressures. A hydraulic motor is supported by the vehicle. The high pressure side or inlet of the hydraulic motor is connected to the water exterior of the vehicle which is at a pressure dependent upon its depth. For example, at a depth of 600 feet, the exterior pressure approaches 275 p.s.i. The discharge side of the hydraulic motor is connected to the container which is at atmospheric pressure or at about 15 p.s.i. The differential pressure across the hydraulic motor then is well over 250 p.s.i. which is quite substantial. As power is needed, water 3,418,818 Patented Dec. 31, 1968 from exterior the vehicle is admitted to the hydraulic motor.

The discharged water from the hydraulic motor eventually fills the container to the point that the pressure within the container approaches that of the Water at the depth of the vehicle. When the container becomes filled with water, according to our invention, the system can be rejuvenated rather easily. We have provided check valve means in an outlet from the container to the water surrounding the vehicle. The cheok valve means can be held shut by a spring aided by the hydraulic force exterior of the container. Before the vessel descends, a slow burning propellant in a water-proof enclosure is placed within the container. A suitable propellant is identified as Amoco Chemical AGF which is an ammonium nitrate base with an asphaltic filler and commercially available from Amoco Chemical Corporation, Seymour, Indiana. When the container is filled with water, the propellant is ignited and will burn at a pressure higher than the ambient water pressure and at a temperature of about 3535 F. This pressure forces the water out through the check valve and in effect readily empties the container of water. At the moment the gas has forced the water out, the gas remaining in the container is at a pressure about equal to that of the surrounding water but at a temperature much higher. The check valve then closes. As the gas cools, the pressure in the container drops rather rapidly until it is well below the pressure of the surrounding water. Thus the container is ready to receive additional water from the discharge of the hydraulic motors and the system has in effect been rejuvenated.

A better understanding can be had from the following description taken in conjunction with the drawings in which:

FIGURE 1 is a sectional elevational view of a vehicle showing the interior components;

FIGURE 2 is a detailed view, partly in cross-section, showing details of a manipulator arm;

FIGURE 3 illustrates the valving and piping arrangement for a hydraulic motor using principles of this invention;

FIGURE 4 illustrates partly in perspective form, a joint of the manipulator arm adjacent the hull of the vehicle.

Referring to FIGURE 1 of the drawings, there is shown a cross-section of the vehicle. The vehicle as shown, has a generally streamline hull or body 10. The upper or forward end of hull 10 is formed by a pressure chamber 12 which is made sufficiently strong to withstand the pressures of the ocean at the depths for which the vehicle will be operating. Chamber 12 forms the operators compartment. In the center or toward the rear of hull 10 is a pressure container 14. This container is likewise constructed of relatively strong material so that it too can withstand the pressures at the depth at which the vehicle will be operating.

At the forward end of the hull and attached to the pressure chamber 12 is a manipulator arm 16 having sections 18 and 20, which are connected by joint 26. Section (or upper arm) 18 is connected to hull 10 by joint 24. The outer end of section (or forearm) 20 is provided with a torque tool 22 which can be a hydraulic motor for rotating the head extension 22A for tightening or loosening bolts or the like. As will be seen in greater detail in FIGURES 2 and 4, joints 24 and 26 provide for movement of the arm in essentially any direction. As will be shown, this movement is accomplished by use of hydraulic power utilized in accordance with our invention.

A Searchlight is provided on the exterior of hull 12 adjacent arm 16 so as to illuminate the area where the manipulator arm is operating. Ports 28 are provided through which the operator can observe movements of the manipulator arm. At the top of pressure chamber 12, there is provided an access way 13 provided with a cover 13A. It is through this access way that the operator enters and exists from the pressure chamber when the vessel is at the surface. Means not shown can be provided for emergency exit of the operator.

Attention is next directed to FIGURE 3 for a better understanding of how the hydraulic pressure of the water exterior of the vehicle is utilized. Shown thereon is a hydraulic motor 55, a valve means 52, low pressure container 14, and manifold 36 through which high pressure water enters.

Hydraulic motor 55 as shown, has a piston 56 reciprocally mounted in a cylinder 49. A piston shaft 59 is provided for taking power from piston 57. A conduit 48 is fluidly connected to interior of cylinder 49 at one end and at the other end conduit 50 is fluidly connected thereto. Thus piston 57 reciprocates in cylinder 49 in accordance with the pressure differential across the piston, This pressure differential is provided by manipulating valve 52 so that one side of the piston is connected to the high pressure water exterior of the vehicle, and the other side connected to the low pressure interior of container 14. By alternating these connections, the direction of the movement of piston 57 can be reversed.

We shall next discuss briefly the description of valve 52. This valve has a cylinder 53 in which is mounted an upper piston 54 and a lower piston 56 connected to handle 64 exterior of cylinder 53 by valve stem 66. (Valve stem 66 should extend through both ends of 53 so as to be pressure balanced.) High pressure water from conduit 36C is connected by conduit 36A to one end of valve chamber 53 and to the other end by conduit 36B. Conduits 48 and 50 connect respectively to intermediate lateral ports 58 and 60 in the wall of valve cylinder 53. Ports 58 and 60 are spaced in relation to the spacing between valve pistons 54 and 56 such that when one lateral port is in communication with the high pressure inlet or manifold 36C, the other lateral port is in communication with the interior of valve cylinder 53 between valve pistons 54 and 56. This interior between these valve pistons is always in fluid communication through center port 61 and conduit 62 with the low pressure interior of container 14. In the position of the valve as shown in FIGURE 3, high pressure fluid enters motor cylinder 49 beneath piston 57 through conduit 50 and forces piston 57 upward; the fluid above piston 57 being discharged through conduit 48, port 58, the interior of chamber 53 between the valve pistons, and through conduit 62 into container 14. To reverse the movement of piston 57 all that is necessary to do is to move handle 64 downwardly so that port 58 is in communication with the high pressure fluid above valve piston 54 and port 60 is in communication with the interior of valve chamber 53 between the valve pistons. Thus it is seen that the piston 57 can be driven in either direction by simple manipulation of valve 52. Although container 14 is shown mounted in an underwater vehicle, it does not have to be associated with such a vehicle. For example, the container can be secured to, or adjacent, an underwater wellhead valve and the associated motor such as motor and control valve 52 (with remote operation not shown) of FIGURE 3 used for the power required to operate such wellhead valve.

The valve and motor arrangement shown in FIGURE 3 is preferably duplicated for each mechanism requiring hydraulic power in the unit. The hydraulic motor is located where the energy is needed and the valve is located in pressure chamber 12 so that the operator can manipulate the valve as necessary. There are shown only three valve control units 32A, 32B and 32C for purposes of simplification although there can be as many control units as needed. Each of these valve control means has two high pressure inlet conduits and one low pressure discharge unit. The two high pressure inlet conduits are connected to header 36 which is connected to the exterior of the vessel. The low pressure discharge conduit is connected to header 38 which is fluidly connected to the interior of container 14. Each of these valves also has two conduits comparable to conduits 48 and 50 of FIGURE 3 for driving a hydraulic motor. As illustrated, valve control 32C is connected through conduits and 72 to motor 74 which is used to drive propeller 76 to provide propulsion of the vehicle. While on the subject of propulsion it might be well to mention that if desired the vehicle can be raised and lowered by means of a cable 78 and propulsion means 76 then used to manipulate the vehicle into exact position. Of course, if desired, auxiliary ballast tanks can be provided in a known manner so that the vehicle can be raised and lowered by contained control equipment within the vehicle itself.

As shown in FIGURE 2, manipulator 16 has four hydraulic motors. These include torque motor 22 for drive torque extension head 22A. Power conduits 40 and 42 for torque motor 22, are connected to a suitable valve such as valve 32B within pressure chamber 12. Upper arm 18 is provided with a first motor 78 and a second motor 80'. Motor 78 is used to drive forearm 20 about axis 20A which is fixed to arm 18. This is accomplished by having a rack means 82 connected to the piston shaft of piston 84 within the cylinder of motor 78. The gears of rack 82 mesh with the circular gears 86 of arm 20. Thus movement of piston 84 rotates arm 20 about axis 20A of upper arm 18. Hydraulic conduits 44 and 46 are connected to the interior of motor chamber 78 on opposite sides of piston 84. These conduits 44 and 46 are connected to a valve means within pressure chamber 12 such as valve means 52 of FIGURE 3.

Means will now be discussed for rotating upper arm 18 with respect to shoulder arm 88. This includes circular gear 93 on the end of arm 88, a rack gear 90 meshing with gear 93 and connected to piston 92 within the cylinder of motor 80 of arm 18. This motor means also has two conduits 94 and 96 similar to conduits 44 and 46, and are also connected to a suitable valve control means in pressure chamber 12. Movement of rack 90 causes arm 18 to rotate about axis 91 which is the center of gear 93.

Occasionally it is desired to rotate the manipulator at right angles to that position shown in FIGURE 1. This is accomplished by provided means to rotate shoulder arm 88 in relation to hull 10. This is accomplished by having a gear rack 98 as shown more clearly in FIGURE 4 meshing with circular gear 100 which is fixed to shaft 88. Rack gear 98 is connected at one end to a first piston 102 and at the lower end to a second piston 104. Piston 102 is in an upper housing 106 and piston 104 is in a lower housing 108. For explanation of operation, it can be considered that housings 106 and 108 correspond to housing 54 of FIGURE 3, and pistons 102 and 104 correspond to the single piston 56. Thus conduits 110 and 112 which connect to cylinders 1'06- and 108, respectively, correspond to conduits 48 and 50 of FIGURE 3. The cylinders 106 and 108 of FIGURE 4 are fixed to the hull of pressure chamber 12.

As rack 98 is moved, gear 100 is rotated which also rotates shoulder arm 88. As the axis 91 of gears 93 is fixed with respect to arm 18, then rotation of gear 93 rotates shaft or axis 91 which also turns arm 18.

It is thus seen that we have provided means utilizing the high pressure of the water exterior of the vehicle to drive hydraulic motors which can be controlled by an operator within the pressure chamber 12. The discharge of these motors is into the low pressure container 14. The amount of power which can be obtained from the use of a rather small container 14 is rather large. For example, it is known that one can obtain 3.2x l0 hp. per cubic ft. of space/ft. of water depth. Thus a cubic foot size container 14 at 500 ft. depth is able to provide 0.016 hp. for 1 hour. This horsepower is seen to be of fairly large magnitude especially when considered that container 14 can be made fairly large such as for a practical value up to at least about 100 cubic feet or more, of course the size depends upon the overall design and engineering of the vehicle.

It is recognized that after a while container 14 will fill up and will no longer be able to receive discharged water from the hydraulic motors. When this occurs we have provided means that can be used for rejuvenating emptying the container 14. This includes several enclosures 112A to 112n of relatively slow burning propellants which develop very large volumes of gas at very high temperatures. A particularly suitable propellant is identified as Propellant AGF supra. This will burn to develop gas at an average temperature several hundred degrees higher than that of the sea water at the depth of the apparatus. When this pressure exceeds the pressure of the water 114 in container 14 it forces valve 116 open. This valve 116 will now be briefly described. It closes an opening 118 in the lower end of container 14. Valve plate 116 sets in well 120 in the lower side of the vehicle. It is held closed by bow springs 122 connected to stem 124. As the vessel or vehicle descends into the water the high pressure of the water also tends to keep valve plate 116 closed. However, when the propellant is burned a pressure is generated which exerts a force on the inside of valve 116 which greatly exceeds the closing force on valve 116 exerted by the water exterior of the vehicle and springs 122. This forces the valve open and also forces the water within container 14 out through such opened valve.

When valve 116 is open, fluid within container 14 is expelled until the pressure inside container 14 is reduced to the approximate pressure to that exterior of the vehicle; at this time springs 122 close valve 116. If the propellant burned has been of a sufficient amount, about all that is left of container 14 at this time is high temperature gas at the approximate pressure of the water exterior of the vehicle. As the temperature of the gas in container 14 is much higher than that of the surrounding water, the gas in the container 14 will begin to cool. Cooling fins 126 are provided which extend through the walls of container 14 to aid in this cooling. As the gas cools its pressure is reduced to a pressure considerably less than that of the surrounding water. The container 14 can then be said to be rejuvenated and additional power can be obtained from the hydraulic motors in a manner described before. This rejuvenation can be repeated many times and is illustrated by the several enclosures 112A to 11221 of propellants. These propellants are ignited by the operator by closing switch 113 which is located in pressure chamber 12. It is to be understood of course that the rate of burning of the propellant, the temperature to which the gas rises, the temperature of the surrounding water all affect the degree of rejuvenation of the power system.

Exploratory work has shown that propellants can be used to generate high temperature gas from a container against a head of water. In one experiment, 6 /2 lbs. of propellant (Amoco AGE) were ignited in a tank full of water at a pressure of about 500 p.s.i. which approximates the pressure of sea water at 1,000 feet. The propellant used was a slow burning propellant and burned for 2.5 minutes during which time 18.5 gallons of water were discharged while the pressure within the tank was maintained at 500 p.s.i At the time the 18.5 gallons of water were expelled, the estimated average temperature of the gas was 275 F. After the gas cooled to 60 F., the gas pressure was 350 psi. This drop in pressure allows 53,000 l t-pounds of work to be done before the pressure is raised to 500 p.s.i. Experience has further shown that the use of a faster burning propellant can be obtained by igniting the propellant at the mid-point, thus the burning rate can be doubled and the average temperature of the gas in the chamber while water is being expelled will be much higher; thus a lower pressure within the vessel will result when the temperature drops to ambient.

The system which we have described is useful for a wide range of power rate usage. A small amount of energy can be used over a long period of time, or a large amount of energy can be used in a short time. Conversely, a large or small force can be applied with the manipulator for unlimited periods of time with no expenditure of energy at all. This last feature is ditficult to accomplish with most other type energy systems.

While the above embodiments have been described with a certain amount of detail, it is to be understood that various modifications can be made thereto without departing from the spirit and scope of the invention.

We claim:

1. An underwater apparatus for obtaining power from the hydrostatic head of a body of water and having a support means which comprises:

a container having an internal pressure independent of said hydrostatic head, said container supported by said support means;

a hydraulic motor means supported by said support means and having an inlet and an outlet;

first conduit means connecting the inlet of said hydraulic motor means to the exterior of said underwater apparatus;

second conduit means connecting the outlet of said hydraulic motor to the interior of said container.

2. An underwater apparatus as described in claim 1 in which said container has outlet means to the exterior of said underwater apparatus; a valve in said outlet means which opens when the diiferential pressure between the interior of the container and the exterior of the container reaches a given value and means for increasing the pressure within said container so that said valve opens.

3. An apparatus as defined in claim 2 wherein said means for increasing the pressure includes means for placing a propellant within said container and means for firing said propellant.

4. An underwater apparatus as described in claim 2 which said hydraulic motor comprises a double acting motor having a piston and a shaft within a cylinder and;

valve means for connecting each end of said double acting motor selectively to said first conduit means and to said second conduit means.

5. An apparatus as defined in claim 3 including cooling fins extending through the wall of said container.

6. An apparatus as defined in claim 3 including manipulator means mechanically coupled to said hydraulic motor means.

7. An apparatus as defined in claim 6 in which said manipulator means includes at least a first section and a second section;

an axle supported by said first section;

a circular gear fixed to said second section and rotatably supported by said axle;

a rack gear meshing with said circular gear;

a hydraulic cylinder having a piston therein which is connected to said rack gear;

valve means for selectively connecting the interior of said motor cylinder to said first conduit means and the other end to said second conduit means. 7

8. An apparatus as defined in claim 6 in which said valve means includes:

a cylinder housing having a central lateral port, two intermediate ports, one on either side of said central port, and two end ports;

a piston shaft extending through one end of said housing and attached to a first piston valve and a second piston valve within said housing, said piston valves being spaced apart the approximate distance as the longitudinal spacing of said intermediate ports,

said central port being connected to said container, said end ports being connected to said first conduit means so as to communicate with the exterior of said underwater apparatus, one' intermediate port being connected to one end of said hydraulic motor means and the other intermediate port connected to the other end of said motor means.

9. A method of obtaining hydraulic power in an underwater apparatus having a container with a relief valve and a hydraulic motor having a first port and a second port for power input and discharge outlet which comprises:

connecting the first port of said motor to the exterior of said vehicle and the second port to the interior of said container;

forcing water out of said container when said container approaches the pressure of the surrounding water at a depth at which the vehicle is operating by igniting a propellant to generate a gas at a temperature and pressure in excess of that of the surrounding water whereby water is forced out through said relief valve of said container by such gas until such pressure in said container equalizes that of the exterior so as to permit the relief valve to close and upon cooling of the gas to have a container having lower pressure than that of the surrounding water.

10. A method of obtaining hydraulic power in an underwater apparatus having a hydraulic motor and a container whose internal pressure is less than the hydrostatic head of the body of water at the level the underwater apparatus is positioned, which comprises:

applying the hydrostatic head to said hydraulic motor;

connecting the discharge outlet of said hydraulic motor DAVID J. WILLIAMOWSKY, Primary Examiner.

the hydrostatic head of the body of water and having a support means which comprises:

a container supported by said support means and having an internal pressure less than the hydraulic head at the level of the container;

a hydraulic motor means supported by said support means;

means for applying the hydrostatic head of said body of water to said hydraulic motor means; second means connecting the outlet of said hydraulic motor means to the interior of said container.

References (Iited UNITED STATES PATENTS 5/1936 Romano 61-69 1/1965 Shatto.

J. K. BELL, Assistant Examiner.

U.S. Cl. X.R. 

